A refrigeration system typically functions in a continuous cycle, reusing the refrigerant in the system. Three pieces of equipment, an evaporator, compressor, and condenser connected in a loop, are used in the cycle. In the evaporator, cold liquid refrigerant is warmed absorbing heat from a medium to be cooled. As the liquid refrigerant temperature is raised, the liquid refrigerant is evaporated, forming a warm refrigerant vapor. The refrigerant vapor is then piped to the compressor. The compressor mechanically compresses the refrigerant vapor to raise the pressure of the vapor thereby lowering the temperature at which the refrigerant vapor will condense. The hot refrigerant vapor is piped to the condenser where the hot vapor is cooled. This cooling changes the refrigerant back to the liquid state. The liquid refrigerant is then piped back to the evaporator, where the cycle begins over again.
There are many different designs of compressors. All compressors, however, in one way or another, mechanically compress the refrigerant vapor. This mechanical action requires moving parts and the moving parts require lubricating oil.
In a hermetic compressor, lubricating oil is constantly in contact with refrigerant in the compressor of a refrigeration system when the refrigeration system is in operation In some types of compressors, the oil is deliberately mixed with refrigerant in order to cool the compressor components. In other types, the intermixing of the oil and refrigerant is a function of refrigerant blowing by piston rings and the like. Over time, the oil becomes contaminated with entrained refrigerant and with various substances in the refrigeration system such as metal filings and corrosion byproducts This contamination reduces the ability of the oil to lubricate the compressor Additionally, aside from the problem of the reduction in lubricating capability due to entrained refrigerant, the oil must be periodically changed much as in an automobile engine. It is undesirable to have refrigerant contaminant in the oil when the oil is drained from the refrigeration system as it is now known that many types of refrigerant pose a danger to the environment.
It has been well known that oil contamination of refrigerant (as opposed to refrigerant contamination of oil) is a problem, particularly in maintaining the efficiency of a refrigeration system. Devices have accordingly been devised that successfully cleanse the refrigerant of entrained oil. Such devices do not address the problem of residual refrigerant that is left entrained in the oil.
The refrigerants utilized in virtually all current refrigeration systems contain chlorofluorocarbons, which includes chlorine as a key element. It is now known that such refrigerants play a role in the condition referred to as "global warming". Responsive to this, the Montreal Protocol, adopted in 1987, mandated a fifty percent cut in chlorofluorocarbon production by the turn of the century Further regulation by the Clean Air Act of 1990 has moved the phaseout date to zero production by the year 2000. In the interim, it is desirable to continue to utilize existing compressor designs with existing refrigerants while, at the same time, minimizing the release of refrigerant vapor to the atmosphere. Refrigerant entrained in oil that has been drained from a refrigeration system ultimately vaporizes and escapes to the atmosphere. Further, when certain levels of refrigerant entrained in the oil are reached, the oil is classified as hazardous waste. Such classification requires the implementation of stringent and costly disposal methods.
A system for removing substantially all the entrained refrigerant contaminant from the lubricating oil of a refrigeration system would have decided advantages. The purified oil could be removed from the refrigeration system with low refrigerant emissions, or could be forceably pumped into another storage vessel. Oil that is to be drained from the system would be in a readily recyclable condition, would not require handling as a hazardous waste, and would not pose the threat of release of refrigerant vapor to the atmosphere.